1. Field of the Invention
The present invention is broadly concerned with label printing and applying apparatus, and corresponding methods, wherein images such as labels are successively printed on a continuous web using a relatively large rotating impression drum and associated digital print heads; thereafter, the printed web passes through a downstream adhesive applicator and a laser cutting and label application assembly where the individual printed images are laser cut and applied to products. More particularly, the invention is concerned with such apparatus and methods wherein use of an improved drum/digital print head printing assembly which permits high speed, on-demand production of images for labels or the like, using relatively inexpensive, thin, lightweight webs.
2. Description of the Prior Art
Traditionally, pressure sensitive labels have been produced using more or less standard, multiple-tower web-fed printing apparatus followed by mechanical die cutting of the individual labels. In such operations, it has generally been necessary to releasably adhere the printed web to a carrier sheet so as to permit die cutting of the labels. Once the labels are cut, the matrix is removed from the carrier, leaving the labels spaced on the carrier sheet which was then formed into a roll. Carrier sheets of this type typically represent nearly one half of the material cost of label production. This is a tremendous waste of resources, and the spent carrier sheets also present an on-going trash disposal burden, typically ending in landfills.
In response to these problems, it has been suggested in the past to employ laser cutting devices in lieu of traditional die cutting systems. Moreover, some laser cutting systems are xe2x80x9clinerlessxe2x80x9d in that the use of carrier sheets is eliminated. For example, U.S. Pat. No. 5,681,412 describes a modern-day laser cutting label production system of this type.
While such laser systems are a significant advance in the art, some problems remain. For example, the upstream printing of label stock prior to laser cutting has not heretofore been seriously addressed in prior laser-based systems. That is, traditional printing methods, be they either web fed multiple-tower printers or even digital printing equipment, it is usually necessary to employ relatively thick webs having sufficient mechanical strength to withstand the printing operation. Rollers or other devices used to pull the webs through these printing units impose significant stresses on the webs, and if the webs are too thin or otherwise insufficiently strong, the webs have a tendency to break and/or elongate which is inimical to consistent quality printing. As a consequence, it has generally been necessary to employ web having a thickness of at least about 2 mils. These webs are relatively expensive, as compared with thinner webs of, e.g., 0.5 mil thickness.
It has also been suggested to avoid intermediate collection of printed and cut labels by use of in-line, complete systems wherein a starting label stock is printed, adhesive is applied, and the cut stock is applied to products. Here again though, these systems suffer from many of the foregoing problems. Furthermore, such complete systems lack desirable on-demand characteristics i.e., the use of conventional printing equipment makes it very difficult to rapidly shift between different types or styles of labels, and cannot produce infinitely variable label copy and shape.
The present invention overcomes the problems outlined above and provides improved label printing and application apparatus especially (although not exclusively) suitable for label making coupled with immediate in-line application of the labels to products. Broadly speaking, the label printing and applying apparatus of the invention includes a web printing assembly operable to print individual label images on a continuously moving web, where the images may be successive or identical, or variable image-to-image. The apparatus includes a rotatable impression drum presenting an outer surface and at least one (and usually plural) digital print heads adjacent the drum outer surface. A downstream web cutting and applying assembly including a laser cutter and a label application device also forms a part of the overall apparatus. Finally, a web guidance system operable to guide a continuous web around at least a portion of the drum surface and between the drum surface and print head(s) is provided, allowing printing of successive images on the web. In practice, with the apparatus of the invention, use can be made of relatively thin, inexpensive webs. This stems from the fact that during printing, the linear speed of the web and the speed of the impression drum surface are closely matched so that there is essentially no relative movement between the drum surface and web. Consequently, the web is stabilized during printing and is not subjected to undue tension or forces which would otherwise distort the web. By the same token, use of digital print heads and associated sensors permits very accurate registration printing so that high quality images can be produced.
In preferred forms, the print head may be inkjet or laser print head, or any other suitable digitally-controlled printing device. The impression drum is preferably rotatable in opposite directions as desired, so that either side of a web may be printed.
Various types of label-applying devices can be used in the invention, such as rotary or in-line units. The only qualification is that a given device be capable of picking up the successive laser cut label images and transferring onto respective products.